Photography Forum

If you mean High Dynamic Range, it is best to use your camera's autobracketing function to take several shots of the same image at different exposures. This extends the dynamic range (tonal range) you can capture. (A tripod helps make it easier to align the images precisely later.) Then you blend them together in an image editor, taking the highlights from one, the shadows from another etc. There is software available which will do this for you, for instance Photomatix.

In order for detail to be shown in all the tonal areas, the dynamic range actually has to be compressed or normalised during the post processing, this may result in an artificial looking picture because of the reduction in difference between light and shade which some people like and some don't. It is also possible to process a single exposure in this way to bring out more detail in the shadows and highlights.

To an extent I think the term HDR is a misnomer. The dynamic range of real life scenes will usually exceed that of any photographic reproduction, the only way to genuinely increase the dynamic range of the viewed photograph is to use a higher dynamic range reproduction medium such as a backlit transparency. As for printed output, the best I have ever seen is a sunlit glossy cibachrome, the luminosity of this medium in direct sunlight is quite breathtaking due to its highly reflective polyester base. However it is also true of all prints that the brighter the lighting the greater the contrast (dynamic range) and the more details will be revealed to the eye. So nearly all photographs benefit from being viewed in bright sunshine or similar strength lighting.

Here you get good tips:
http://hdrlabs.com/

I think HDRI will be the future of digital images.

Look here:
http://en.wikipedia.org/wiki/High_dynamic_range_imaging
it is explained in details

I have been working with HDR this summer with interesting results will continue to play with it